Aspects of the following description are directed to a mold cased circuit breaker (so called abbreviated MCCE) for protecting a circuit against an electrical overload by forcibly interrupting the circuit, and more particularly to a mold cased circuit breaker capable of forcibly separating a contact during a circuit fault by allowing a user to easily notice a state of the contact.
Typically, circuits are disposed at one side thereof with a mold cased circuit breaker for protecting the circuit against an electrical overload.
Referring to FIG. 1, a conventional mold cased circuit breaker incorporates a cover (1), a base (2), a switching mechanism (3) for opening and closing a circuit, a tripping device (4) for detecting a circuit fault, and an arc extinguisher (5) for extinguishing electrical arc jumps generated at contacts during a circuit interruption.
Referring to FIG. 2, the switching mechanism (3) principally incorporates a side plate (111) fixed at a cover, a pair of stationary contactors (112) disposed at a circuit, a lever (113) rotatably disposed at the side plate (111) and formed with a reset pin (113b), a handle (114) integrally disposed at an upper end of the lever (113) for displaying each circuit condition and allowing a user to manipulate, a latch (115) limited in a rotating angle by the reset pin (113b) to rotate within a predetermined angle, a latch holder (116) selectively restraining the latch (115), a nail (117) controlling the latch holder (116), an upper link (118) rotatably connected to the latch (115), a lower link (119) connected to the upper link (1118), and a shaft unit (122) disposed with a pair of movable contactors (124) selectively connected to the stationary contactors (112) by the operation of the lower link (119).
Referring to FIG. 2, in one aspect of the conventional mold cased circuit breaker, the handle (114) is aligned on a tripped position and the stationary contactors (112) and the movable contactors (124) are separated in a tripped condition, under which there is no particular force that is activating thereon.
If the circuit breaker is reset to completely interrupt the circuit in the tripped state as shown in FIG. 2, the handle (114) is rotated clockwise to allow the circuit breaker to undergo a reset state as shown in FIG. 3. In this case, the circuit breaker is not instantly manipulated into a closed state from a tripped state (The handle is in a closed position, and the stationary contactors and movable contactors are in engagement therebetween. See FIG. 4) for being conducted again, but the circuit breaker is manipulated into a reset state (The handle is in a reset position, and the stationary contactors and movable contactors are in the state of being engaged) before being manipulated into a closed state.
If the handle (114) is rotated clockwise to be in a state as shown in FIG. 3, the reset pin (113b) of the lever (113) rotates the latch (115) to cause a right end of the latch (115) to go downward, where the upper link (118) and the lower link (119) are rotated at the same time. At this time, current still does not flow as the lower link (119) is hinged only to a shaft unit (122), whereby the shaft unit (122) is not rotated.
If the circuit breaker is manipulated into a closed state for being conducted, i.e., if the handle (114) is rotated counterclockwise to be positioned in a closed state and the stationary contactors and movable contactors are in the state of being engaged, current flows as the circuit breaker comes to be in such a state as shown in FIG. 4. The latch (115) in a reset state (when the circuit is interrupted) as shown in FIG. 3 cannot be activated even if the handle (114) is completely moved counterclockwise as the latch (115) is in a state of being restrained within the latch holder (116). However, if the handle (114) is moved counterclockwise as illustrated in FIG. 4, a main spring of the lever (113) pulls a toggle pin (120) to rotate the lower link (119) counterclockwise and to rotate the shaft unit (122), whereby the stationary contactors and movable contactors are in the state of being engaged to allow the current to flow.
If the mold cased circuit breaker is in a normal state, and when the handle (114) is forced to rotate clockwise as depicted in FIG. 4, the stationary contactors (112) and movable contactors (124) should not maintain a state where both contactors (112, 124) are engaged as shown in FIGS. 5 and 6.
In other words, if the handle (114) is in a closed position and is rotated clockwise to allow the molded case circuit breaker to be in a tripped state or in a reset state while the stationary contactors (112) and movable contactors (124) maintain a state where both contactors (112, 124) are engaged as shown in FIG. 4, the movable contactors (124) must rotate to separate themselves from the stationary contactors (112). In other words, if the stationary contactors (112) and movable contactors (124) are in the state of being engaged, the handle (114) should not be in a tripped position as shown in FIG. 5, or the handle (114) should not be in a reset position as shown in FIG. 6.
For example, as illustrated in FIG. 5, the stationary contactors (112) and movable contactors (124) may be in a fused-like state by an accident current or may not be separated due to other causes to allow the handle (114) to be positioned on a reset state, but the stationary contactors (112) and movable contactors (124) may be in a state of being engaged. However, if the stationary contactors (112) and movable contactors (124) are in a state of being engaged, the handle (114), which is a means for indicating a circuit state, should not be in a tripped position or a reset position.
Even if the handle (114) is rotated to a state shown in FIG. 5, but is nonetheless unable to separate the stationary contactors (112) from the movable contactors (124), the handle (114) may indicate a reset position indicative of a circuit being opened, but the stationary contactors (112) and movable contactors (124) are in fact engaged for being in a conductive state. Under this circumstance, if an operator happens to work on the circuit, assuming that the circuit is not in a conductive state based on a fact that the handle (114) is in a reset position, the operator may be struck by electricity during the work.
In a nutshell, if the stationary contactors (112) and movable contactors (124) are not separated due to a fused-like engaged state and if the handle (114) indicates a tripped position or a reset position, the stationary contactors (112) and movable contactors (124) should be forcibly separated, but the conventional mold cased circuit breaker thus described suffers from a drawback that an actual circuit state and a handle-indicating state are different to thereby cause a safety failure problem.